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HANDBOOK OF PHVSIOLOGV 



CIRCULATION I 



OS 



FIG. 56. Potential distribution in the cross section of a 

 thorax, calculated from the surface time-voltage areas of 

 QRS of normal hearts. The figures indicate the amount of 

 time-voltage area as fractions of the maximal area, recorded with 

 unipolar electrodes at given points on the thoracic circum- 

 ference. The null line is strongly curved. The shaded parts 

 show those areas which contain relatively high voltages. [From 

 Bockh & Schaefer (118).] 



TABLE 5. Spatial, Azimuthal, and Elevational Angles of 

 QRS and T Areas, and Ventricular Gradient* 



* Measured according to fig. 58D. Magnitudes are given 

 in microvolt-sec. The group of 18 normal young men is 

 rather small, but no larger series is available in the literature. 

 [From Simonson el al. (459).] 



all information to be gained from a vectorial analysis 

 doubtlessly is the record of the vector loop. 



The Vector Loop 



The vector loop (4, 7, 12, 15, 25, 28, 35, 37, 59, 

 72, 109, 247, 385, 386) does not reveal any new 

 information which could not be gained by detailed 

 analysis of conventional ECG records, but it does 

 present such information in a plastic three-dimen- 

 sional and illustrative form. The main handicap for 

 clinical application of vector loops is the fact that the 

 empirical foundation for interpretation is still rather 

 small. 



TECHNICAL REMARKS. The practice of vectorcardi- 

 ography, starting with graphical constructions of 

 vectors by Einthoven (183) and later by Mann (332) 

 (who called such constructions "monocardiograms"), 

 soon abandoned these rather complicated procedures. 

 Schellong (59) and, at nearly the same time, Sulzer 

 & Duchosal (475) developed a technique of recording 

 the vector directly in its projection on a plane. If 

 one takes bipolar or unipolar leads, the vectors of 

 which stand perpendicular to each other, but lie in 

 the same plane, and connects these leads to two 

 pairs of plates in a cathode-ray tube, the spot of the 

 oscilloscope follows a curve which describes the time 

 shift in position of the vector peaks relative to the 

 zero point (fig. 57). This curve may be regarded as 

 the chronological summation of all vector peaks 

 during the movement of the heart vector. If this 

 vector loop is timed, e.g., by interruptions of the 

 recording electron beam, the conventional ECG 

 could be reconstructed as a voltage vs. time record, 

 because the projection laws still hold and it is per- 

 missable to apply them in this manner. In recording 

 the loop, a certain ditHculty arises in fi.xing the sense 



TABLE 6. Statistics of Magnitude and Direction of the Frontal Projections of 

 QRS Areas (Aq^s) and Ventricular Gradient (after Ashman) 



[From Kossmann (297).] * 157 adults only. 



